1. Field of the Invention
The embodiments described below are related to wireless communication and more particularly to the determination of non-overlapping cycles during which an access terminal will wake up and communicate with multiple different systems with which it is configured to communicate.
2. Background of the Invention
There are multiple types of wireless Wide Area Networks (WAN's) currently deployed throughout the world. These WAN's are defined by the technology used to communicate with the access terminals operating with the WAN. Historically the access terminals could only communicate using one technology. Eventually dual-mode and dual-band access terminals were developed that could communicate using multiple technologies and/or at multiple frequencies; however, the terminals could only switch between technologies or frequency bands via a hard transition, i.e., when the terminal went out of range of a preferred network, it would be dropped. If the terminal could not re-establish communication with the preferred network, then the terminal would attempt to communicate with another network using another technology and/or a different frequency band.
For example, in the CDMA2000 family of technologies, there are multiple different technologies that can be deployed with a wireless WAN. Code Division Multiple Access or CDMA is a multiple access scheme for digital radio, to send voice, data, and signaling data (such as a dialed telephone number) between access terminals, e.g., mobile phones, and cell sites. In a CDMA system different communication channels are defined with codes (PN sequences). CDMA permits many simultaneous transmitters on the same frequency channel, unlike Frequency Division Multiple Access (FDMA), used in the Advanced Mobile Phone System (AMPS), and Time Division Multiple Access (TDMA), used in Global System for Mobile communications (GSM) and Digital-AMPS (D-AMPS), which use single channel per access terminal or a smaller group of access terminals.
CDMA2000 has a relatively long technical history, and remains compatible with the older CDMA telephony methods, such as cdmaOne, the original CDMA technology. The CDMA2000 family of technologies include CDMA2000 1×RTT and CDMA2000 EV-DO. Each of these are approved are approved radio interfaces and are deployed throughout the world.
CDMA2000 1×RTT, the core CDMA2000 wireless air interface standard, is also known as 1×, 1×RTT, and IS-2000. The designation “1×RTT”, meaning “1 times Radio Transmission Technology”, indicates the same RF bandwidth as the IS-95, or cdmaOne standard, i.e., a duplex pair of 1.25 MHz radio channels. This contrasts with 3×RTT, which uses channels 3 times as wide (3.75 MHz) as the IS-95 channel. 1×RTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to (in quadrature with) the original set of 64 channels defined in the IS-95 standard. Although capable of higher data rates, most deployments are limited to a peak of 144 kbit/s. 1×RTT also made changes to the data link layer for the greater use of data services, including medium and link access control protocols and Quality of Service (QoS). The IS-95 data link layer only provided “best effort delivery” for both voice and data.
1×RTT officially qualifies as 3rd Generation (3G) technology, but it is considered by some to be a 2.5 G, or sometimes 2.75 G technology. This actually allows it to be deployed in 2G spectrum in some countries that limit 3G systems to certain bands.
CDMA2000 3× or EV-DO Rev. B uses a pair of 3.75 MHz radio channels (i.e., 3×1.25 MHz) to achieve higher data rates. The 3× version of CDMA2000 is sometimes referred to as Multi-Carrier or MC. The 3× version of CDMA2000 has not been deployed and is not under development at present.
CDMA2000 Evolution-Data Optimized or Evolution-Data Only (EV-DO) is a telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. It employs multiplexing techniques such as CDMA as well as Frequency Division Duplex (FDD) to maximize the amount of data transmitted. It is standardized by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world—particularly those previously employing CDMA networks, as opposed to GSM networks.
The EV-DO feature of CDMA2000 networks is significantly faster than the Enhanced Data Rates for GSM Evolution (EDGE) used by GSM networks. It provides access to mobile devices with air interface speeds of up to 2.4 Mbit/s with Rev. 0 and up to 3.1 Mbit/s with Rev. A. High-Speed Downlink Packet Access (HSDPA), a competing technology for Wideband Code Division Multiple Access (W-CDMA), Rev A modems have the ability to maintain both circuit switched voice and packet data calls from the same radio. It provides an IP based network. There have been several revisions of the standard, named alphabetically starting with the first as Rev. A (“revision A”), while the first standard is referred to simply as Rev. 0.
Rev 0, the initial design of EV-DO, was developed in 1999 to meet requirements for a greater-than-2-Mbit/s downlink for stationary communications, as opposed to mobile communication such as a moving cellular phone. Initially, the standard was called High Data Rate (HDR), but was renamed to 1×EV-DO after it was ratified by the International Telecommunication Union (ITU) and it was given the numerical designation TIA-856, or IS-856.
Rev. A offers fast packet establishment on both the forward and reverse links along with air interface enhancements that reduce latency and improve data rates. In addition to the increase in the maximum burst downlink rate from 2.45 Mbit/s to 3.1 Mbit/s, Rev. A has a significant improvement in the maximum uplink data rate, from 153 kbit/s to a maximum uplink burst rate of 1.8 Mbit/s. This improvement assumes early acknowledgement of the first sub-packet, typical data rates therefore average below 1 Mbit/s.
EV-DO Rev B is a multi-carrier evolution of the Rev A specification. It maintains the capabilities of EVDO Rev A, and provides the following enhancements: Higher rates per carrier (up to 4.9 Mbit/s on the downlink per carrier). Typical deployments are expected to include 3 carriers for a peak rate of 14.7 Mbit/s; higher rates by bundling multiple channels together enhances user experience and enables new services such as high definition video streaming; statistical multiplexing across channels to further reduce latency, enhancing the experience for latency-sensitive services such as gaming, video telephony, remote console sessions and web browsing; increased talk-time and standby time; hybrid frequency re-use, which reduces the interference from the adjacent sectors and improves the rates that can be offered, especially to users at the edge of the cell; efficient support for services that have asymmetric download and upload requirements, i.e. different data rates required in each direction, such as file transfers, web browsing, and broadband multimedia content delivery.
For clarity, various aspects of the techniques are described below for a High Rate Packet Data (HRPD) system that implements IS-856. HRPD is also referred to as Evolution-Data Optimized (EV-DO), Data Optimized (DO), High Data Rate (HDR), etc. The terms HRPD and EV-DO are used often interchangeably. As mentioned, currently HRPD Revisions (Revs.) 0, A, and B have been standardized, HRPD Revs. 0 and A are deployed, and HRPD Rev. C is under development. HRPD Revs. 0 and A cover single-carrier HRPD (1×HRPD). HRPD Rev. B covers multi-carrier HRPD and is backward compatible with HRPD Revs. 0 and A.
While the above technologies are deployed, e.g., throughout North America, they are not necessarily uniformly deployed and may be deployed in an overlapping manner. For example, certain areas may have HRDP Rev0 deployed, while others may have Rev. A., and both can be deployed in an overlapping fashion with a 1×RTT deployment.
Accordingly, it would be preferable to be able to execute a soft transition from one network to another. In other words, it is preferable to deploy a hybrid access terminal with multiple radios, or a configurable radio, which can alternatively communicate with various networks. In such a hybrid terminal, however, it will be necessary to ensure that there are not conflicting attempts to use the terminal resources to communicate simultaneously with multiple networks.
For example, conventional access terminals are designed to enhance their battery performance by ensuring that they only monitor the network periodically. In other words, when the terminal is in active, it will typically enter a sleep mode and awake periodically to check in with the network. The exact periodicity and time at which the access terminal and the network communicate with each other is typically defined by the associated standard. This is commonly known as “slotted mode of operations”. Accordingly, in a hybrid terminal it will be important to ensure that the terminal does not simultaneously attempt to wake up and access multiple networks.